An air mattress is a mattress that has a plurality of air cells extending to the bed width direction and being arranged in parallel in the bed longitudinal direction and is provided with cushioning properties by supplying the art to each air cell and inflating and inflating each air cell (Patent Document 1). There has been a kind of air mattress which is controlled so that the air cells are alternately inflated and deflated one to another. This configuration makes it possible to effectively prevent the bed user from getting bedsores compared to the case where the bed user is lying on the air mattress continuously. In this alternate inflation and deflation, for a plurality of the air cells, every third cell, for example, is repeatedly contracted and expanded at the same timing. That is, for the air cells arranged in the bed longitudinal direction, from all the air cells being inflated, the first air cell, fourth air cell, seventh air cell, . . . are deflated (air-discharged) by reducing the pressure in these cells, then these cells are pressurized (air-supplied) and returned to the expanded state. Subsequently, the second air cell, fifth air cell, eighth air cell, . . . are deflated by reducing the pressure, then these cells are returned to the expanded state by increasing the pressure in these cells. Then, the third air cell, sixth air cell, ninth air cell are placed under the same pressure control. Thereafter, the first and other associated air cells are implemented with same pressure control. Thus, the pressure of the air cells is controlled in this way to alternately inflate and deflate the air cells, whereby it is possible to prevent the bed user from getting bedsores and others.
On the other hand, diaphragm type pumps are usually used to supply and discharge air for air cells. In the diaphragm type pump, the diaphragm is moved reciprocatedly by reciprocate drive of the diaphragm by means of a linear motor for making linear motion, to thereby supply air to the air cells and discharge air from the air cells.